<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title></title>
		<script type="text/javascript">
			//声明
			var name;

			//赋值
			name = "张三";

			//使用
			// alert(name);


			// 初始值
			var myAge = 20;

			myAge = 21;

			myAge = 22;

			// alert(myAge);

			var $a = 1;

			var _b = 2;

			var A = 3

			var a = 4;
			
			// alert(A);
			// alert(a);
		</script>
	</head>
	<body>
	</body>
</html>
